New report shows water on Saturn’s moon

HARI SREENIVASAN: A report published this week in Science magazine offered new remarkable details about the presence of water on one of Saturn's moons. It once again stirred talk about the possibility of life elsewhere in our solar system. For more, we are joined from Los Angeles by David Stevenson of the California Institute of Technology. He co-authored the article.

So tell us about this moon, Enceladus. You knew about it, quite a bit about it before. Tell us what you found and how did you find it?

DAVID STEVENSON: So we knew already that Enceladus has geysers. Water coming out of cracks near the south pole. But we didn't know what was beneath the surface. What we've now done by tracking the Cassini spacecraft, which is in orbit around Saturn, is figure out that there must be excess mass underneath the ice at the south pole. And water will do that because water is more dense than ice. This is an ocean that is about the size of Lake Superior, perhaps even larger and it is about 10 kilometers thick. So it's a lot of water.

HARI SREENIVASAN: Why is this exciting? This is maybe a basic science question – if this planet is further from the sun than we are and it's incredibly cold – a few hundred degrees below zero – how is it possible that water exists there?

DAVID STEVENSON: The way water is produced in Enceladus is by tides. Enceladus is in orbit around Saturn. The orbit is not circular so that as the satellite goes around Saturn is gets flexed and this heats the ice and allows it to melt in part. A similar effect happens in Europa which is a moon of Jupiter.

HARI SREENIVASAN: So is it possible for this to mean that there is life there? I mean water is one of those things that we always look for to see if life can exist right?

DAVID STEVENSON: Yes, that's right. Actually, water is quite common. Water is present in many of the icy bodies in the outer solar system, I suspect, we don't know for sure. I think one of the interesting things about Enceladus, and also Europa, is that that water is likely to be in contact with rock underneath the ocean. And when you have water and rock and energy sources you have chemistry. And so indeed it seems to create a lot of the conditions that we think are suitable for life.

HARI SREENIVASAN:: All right so what happens next? The Cassini spacecraft is going to continue on for a couple of years and do a couple of more flybys of this moon. What are you looking for?

DAVID STEVENSON: Well, certainly it would be nice to get a little more information about Enceladus. We're not going to be more information about the gravity which is the method that we used to reach this result. The Cassini mission will end by coming in very close Saturn – getting inside the rings of Saturn — and that will be really exciting. In 2017 we'll be able to collect additional data about Saturn. As for Enceladus, I think that if we're really going to figure out what's going on there we have to have to be talking about a mission sometime in the future – a decade or so – as indeed we should for Europa as well.

HARI SREENIVASAN: All right David Stevenson from CalTech, joining us from California, thanks so much.